1. Field of the Invention
The present invention relates to a semiconductor device using a fluorinated silicate glass film as an interlayer metal dielectric film, and relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to an improvement in the adhesion between the fluorinated silicate glass film and a silicon nitride film serving as a protective insulation film.
2. Description of the Background Art
In a semiconductor device having a multilayer metal interconnection (a plurality of metal wire layers), a fluorinated silicate glass film (hereinafter simply called “FSG”) is used as an electrical insulation layer (hereinafter called an interlayer metal dielectric film (IMD)) to be interposed between the plurality of metal wire layers.
FIGS. 5A and 5B are cross-sectional views for describing a conventional semiconductor device.
In FIG. 5A, reference numerals 21 and 22 designate metal wire layers; 3 designates FSG serving as an interlayer metal dielectric film formed between the metal wire layers 21 and 22; and 5 designates a silicon nitride film which serves as a protective insulation film (also called a “passivation film”) and is to be laid on the highest layer of the semiconductor device.
In the conventional semiconductor device, the FSG serving as the interlayer metal dielectric film 3 emits free fluorine (not shown). The thus-emitted free fluorine diffuses outward, thus forming fluorine substances. The expression “fluorine substances” used herein designates fluorine itself, contamination precursor components, and fluorine-containing contamination compounds spontaneously generated from the precursor components.
The fluorine substances are accumulated along a boundary surface between the FSG 3 and the silicon nitride film (serving as the protective insulation film) 5.
The silicon nitride film 5 has a strong blocking effect against the fluorine substances, thus preventing diffusion of the fluorine substances. Accordingly, the fluorine substances are accumulated at high concentration along a boundary surface between the FSG 3 and the silicon nitride film 5.
For this reason, there is a chance of swelling or exfoliation of the silicon nitride film 5 arising.
As shown in FIG. 5B. even in the vicinity of the outer periphery of a semiconductor substrate 1, the fluorine substances are concentrated along the boundary surface of the FSG 3 and the silicon nitride film 5. Therefore, the silicon nitride film 5 is prone to be exfoliated.
As mentioned above, weak adhesion exists between the FSG 3 serving as the interlayer metal dielectric film and the silicon nitride film 5 serving as the protective insulation film. Therefore, swelling or exfoliation of the silicon nitride film 5 arises, thereby deteriorating the performance or reliability of the semiconductor device.